Method and apparatus for an acoustic-electric channel mounting

ABSTRACT

Method and apparatus for rotational alignment and attachment of ultrasonic transducers to a barrier with one submerged surface uses a temporary transducer assembly to position mounting rings on opposite surfaces of the barrier. Plural permanent transducers are then mounted to each mounting ring and are aligned with each other across the barrier by virtue of the alignment of their mounting rings. The submerged mounting ring is used like a cylinder in combination with a mounting plate for the transducers on the submerged side of the barrier or each submerged side transducer has a suction cup fitting for use to exclude water from between each transducer and the submerged barrier surface to facilitate bonding of the submerged side transducers to the barrier.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.13/559,164 filed Jul. 26, 2012, now U.S. Pat. No. 8,681,587, whichclaims priority on U.S. provisional patent application 61/686,022 filedMar. 29, 2012, which are both incorporated herein by reference.

FIELD AND BACKGROUND OF THE INVENTION

The present invention relates generally to the field of transducers, andin particular to rotationally aligning transducers on opposite sides ofa barrier, and to attaching transducers to submerged surfaces.

A transducer is a device that converts one form of energy to another.Transducers may be used, among other functions, to transmit and receivedata or power across a solid barrier without requiring any holes in thebarrier. Conceptually, this can be done by a first transducer on oneside of a barrier turning electrical energy into mechanical energy, themechanical energy traveling across the barrier, and being received by asecond transducer on the other side of the wall which converts someportion of the mechanical energy back into electrical energy. Thisability is particularly useful for transmitting energy and data throughbarriers like ship and submarine hulls, pressure vessel tanks and otherwalls separating extreme environments where it is often undesirable tocreate openings for wires.

FIG. 9 is partially taken from published patent applicationUS2010/0027379, and shows a pair of axially aligned piezoelectricultrasonic transducers 12 and 16 that are acoustically coupled toopposite surfaces 20 and 24 of a steel wall 22 that may be the hull of aship or submarine or other barrier.

Ideally, ultrasonic communication transducer devices should be attacheddirectly to the communications barrier. It is generally desirable tohave a smooth, uninterrupted, uniform barrier between coupledtransducers.

The attachment of transducers to solid barriers is often simple in drylaboratory or factory environments. Although it may be relatively simpleto affix transducers to the surface of oceangoing vessels when suchvessels are in dry dock, it will sometimes be preferable to installtransducers below the water line without the expense, delay, anddifficulty of moving a large ship out of the water.

Proper transducer attachment is extremely difficult in an underwaterenvironment such as a submerged portion of a ship's external hull,however, for a variety of reasons. First, it is usually desirable toremove all water, as well as any other extraneous substances, from theattachment surface. It is also difficult to apply and retain epoxy orother adhesives in an underwater environment, and to provide theconditions necessary for such adhesives to harden or cure properly. Itis often necessary to provide a sustained loading force at theattachment site while an epoxy or adhesive sets, which poses additionalchallenges when the surface is submerged. Thus, there is a need forapparatus and methods for removing and excluding water from a submergedtransducer attachment surface, for applying adhesives to submergedattachment surfaces, and for applying sustained pressure to suchsurfaces to allow adhesives to set. It is particularly desirable to haveapparatus and methods for both direct attachment of transducers tounderwater substrates, and for attachment utilizing an intermediarylayer.

Furthermore, it can be difficult to align transducers on opposite sidesof a surface, such as the hull of a large ship or a submarine, when onlyone side of the surface can be seen at a time. Techniques have beendeveloped to positionally align transducers across a ship's hull usingsignal peaking at a single point. See WO2011/027168 and WO2011/027169,both to Bagshaw et al. Single point peaking techniques are not wellsuited, however, for aligning a plurality of transducers in a singlecompact arrangement through a hull because such arrangements must bealigned axially as well as positionally, and rotational alignment cannotbe determined using a single peaking point. Thus, it is desirable tohave a convenient method for determining rotational alignment across ahull using a plurality of peaking points corresponding to a plurality ofspaced transducers.

Transducers may be mounted to communications surfaces such as hullseither directly, typically one at a time, or using an intermediary layerwhich may carry multiple previously-configured transducers.

Direct attachment is the preferred coupling method. Direct attachmentminimizes the number of interfaces between transducers on opposite sidesof the barrier, which results in greater transfer efficiency and lessinterference. Hull curvature can cause variations in the thickness ofthe adhesive layer between flat transducers and plates, and roundedcommunication surfaces they are attached to. Any curvature of thecommunication surface is less significant using direct attachmentbecause each transducer will have a smaller area than a largerintermediary plate.

It can be difficult to align multiple directly attached traducers acrossa barrier because direct attachment is often done one transducer at atime. Thus, methods for aligning multiple transducers being mounteddirectly to a submerged hull are needed. Direct attachment can also bedifficult because individual transducers, such as piezoelectriccrystals, are often fragile. As a result, handling individualtransducers, and holding them against the communication surface duringadhesion, risks breaking the transducers.

Attachment using an intermediary layer, such as transducers on top of ametal plate, is easier because multiple transducers can be attached tothe single plate in precise alignments in a factory setting. It can beeasier to align two intermediary plates across a hull, each platecarrying several transducers, than to align a large number of individualtransducers, two at a time in the field. An intermediary plate can alsocarry all the electronics that are needed to be attached to thetransducers it carries. This avoids the difficulty of trying to attachelectronics to transducers, underwater, after they have been mounted toa ship. It can also be easier to handle fragile transducers that arepre-mounted on a durable metal plate because any pressure requiredduring the adhesion process can be placed on the intermediary plateinstead of on the fragile transducers themselves.

The main disadvantage of using an intermediary plate is that signalstraveling between transducers must cross a greater number of interfaces,increasing signal reflections and interference. Thus, transducersmounted on intermediary layers may be less efficient. It is alsodifficult to achieve minimal and uniform adhesive thickness between aflat intermediary plate and a curved communication surface because anintermediary plate will have a greater surface area than individualtransducers. This excess adhesive may also reduce transducer efficiency.

SUMMARY OF THE INVENTION

The present invention overcomes several serious difficulties posed whiletrying to align and attach transducers on opposite sides of a barrierlike a submarine hull or the like, when the vessel is in a body ofwater, or other barriers where one or both sides of the barrier may bein a hostile, e.g. under high pressure, high temperature or nuclearconditions, or a liquid environment.

The invention solves these obstacles is significant part by usingmounting members, which preferably take the form of rings havingthreaded bolt holes at their periphery. Methods and apparatus arepresented for rotationally aligning mounting rings on opposite sides ofa hull using a temporary, removable plate having multiple temporarytransducers. Peaking methods are used to locate the plurality oftransducers with respect to the opposite side of a wall, such as aship's hull. The mounting rings can be aligned across the wall using theknown relative locations of the plurality of transducers.

Rotational alignment of mounting rings across the hull makes itrelatively simple to align permanent transducers within each ring withcorresponding transducers within the mounting ring on the opposite sideof the wall. Without rotational alignment, is it difficult or impossibleto align multiple transducers within a small area of the hull wall.

Preferably, ring alignment is achieved by employing a temporaryalignment plate having a plurality of spaced, temporary transducers.

Preferably, the alignment plate is easily added and removed to mountingsrings by screws or bolts, and may be reused.

The mounting rings are round, resembling a thin section of a hollowcylinder, and have approximately six threaded bolt holes spaced evenlyabout their perimeter, although more or less holes can be used.

This invention also provides methods and assemblies for attachingtransducers directly to submerged surfaces, and also for attaching anintermediary plate holding multiple transducers to a submerged surface.Both the direct attachment methods and the intermediary plate methodsutilize previously aligned mounting rings having threaded bolt holes attheir periphery.

The mounting methods provide means for removing water from the submergedsurfaces, preferably within a section of the hull defined by a mountingring.

The mounting methods provide means for using epoxy or other adhesives toattach transducers and transducer assemblies to submerged surfaces,preferably to a section of the hull within the circumference of amounting ring.

The various features of novelty which characterize the invention arepointed out with particularity in the claims annexed to and forming apart of this disclosure. For a better understanding of the invention,its operating advantages and specific objects attained by its uses,reference is made to the accompanying drawings and descriptive matter inwhich preferred embodiments of the invention are illustrated.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a top perspective view of a mounting ring of the invention;

FIG. 2A is a top perspective view of a mounting ring with an attachedalignment plate;

FIG. 2B is a partial sectional view taken along line 2B-2B of FIG. 2A ofthe mounting ring with an affixed mounting plate and peakingtransducers;

FIGS. 3A to 3D are four depictions of the same sectional view of amounting ring affixed to a wall, each depicting an engaged mountingplate in a different position, and illustrating a different step forremoving water from a cavity between the mounting plates and the wallusing the mounting plate as a piston;

FIG. 4A depicts the top side (left) and FIG. 4B the bottom side (right)of an intermediary plate for mounting four transducers to a submergedsurface;

FIG. 5 depicts a top perspective view of an assembly for mounting amounting plate on a submerged wall including a mounting plate, amounting ring, a pressing plate, and the wall;

FIG. 6A depicts a top perspective view and FIG. 6B a sectional viewtaken along line 6B-6B of a backing and flange for mounting a transducerdirectly on a submerged hull and, in the sectional view only, atransducer under the backing;

FIG. 7 depicts a radial cross-sectional view of an assembly for mountinga transducer directly on a submerged hull before the backing andtransducer are fully pressed against the hull;

FIG. 8 depicts the same sectional view as FIG. 7, corresponding to line8-8 of FIG. 10, after the backing plate has pushed the backing, flange,and transducer towards the hull;

FIG. 9 is a schematic diagram of piezoelectric transducers aligned onopposite sides of a steel ship hull;

FIG. 10 show a backing plate bolted to the top of a mounting ring on aship surface, and flow tubes entering the backing plate at four pointsto contact four transducers (not visible) directly mounted on the shipsurface below; and

FIG. 11A shows a pressing plate connected to a mounting plate by screwsand springs before (left) and at FIG. 11B, after (right) the pressingplate pushes the mounting plate into contact with the hull surfacebelow.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, in which like reference numerals are usedto refer to the same or similar elements, FIG. 1 shows a mounting ringor member 10 of the invention having threaded bolt holes 11 arrangedabout its periphery. In an embodiment of the invention the ring 10 hassix threaded bolt holes 11 spaced evenly around its circumferencealthough more or fewer bolt holes can be used. Shapes other than roundrings and other arrangements of threaded bolt holes are possible.Typically the side of the ring 10 lacking holes will be affixed, such asby welding or maritime adhesive, to a ship's hull or the surface ofanother barrier.

A diagram of a steel ship's hull 22 having two surfaces 20 and 24, andtransducers 12 and 16 aligned on opposite sides of the hull 22, is atFIG. 9.

FIGS. 2A and 2B show two views of an alignment assembly 13 fordetermining the translational and rotational position of a mounting ring10 through the thickness of a wall or barrier 22. The alignment processpreferably begins with a mounting ring or member 10 fixed to one side 20of the wall 22 that the transducers are to communicate through.

The wall may be of any material that will allow transducers to conveyenergy and/or information between one another, but will often comprisemetal, e.g. steel, and may be part of a sea craft. If one side of thewall is submerged—being the outside of a submarine, for example—it ispreferable that the first mounting ring be fixed to the submerged side.This will make it easier to perform the peaking process, which must bedone from the side of the wall opposite the alignment assembly and thefirst mounting ring, understanding there will be no line-of-sight to theoutside of the wall to help with aligning the opposite mounting ring.

A temporary alignment plate 40 is removably fixed to the periphery ofthe outside mounting ring 10. This attachment may be accomplished bybolts 42 or screws threaded into each of two bolt holes 11 in themounting ring 10, although any reversible attachment method may be used.

The temporary alignment plate 40 includes a plurality of ultrasonictransducers 44 spaced along the length of the plate 40. In a preferredembodiment the plate includes two transducers, although more may also beused. The transducers 44 are preferably connected to the plate 40 bybolts 46.

The assembly 13 is adapted so that the positions of each the pluralityof transducers 44 may determined from the opposite, inside surface 24 ofthe wall 22 using a peaking technique to locate each of the severaltransducers. This is done by moving a signal receiving transducer 45along the inside surface 24 of the wall in the general location of theoutside mounting ring 10 that can be estimated without actually seeingthe outside ring until a maximum signal is detected at one of theoutside transducers 44. This will be the location at which the insideand outside transducers 44 and 45 are aligned so that a mark 47 isplaced on the inside surface 24 at this location. The process is thenrepeated to mark the location of the other transducer 44.

With both positions of the transducers 44 marked on the opposite insideof the wall 24, both the location and the rotational alignment of theoutside mounting ring 10 can then be determined from the opposite side24 of the wall by comparing the location of the plurality of transducers44 and their known and marked relationship relative to the outsidemounting ring 10, the bolt holes 11, and the alignment plate 40.

Using this information, it is then a simple matter to attach a secondmounting ring 10 to the opposite inside 24 of the wall 22 so that it hasthe same location and rotational alignment as the outside mounting ring10 on surface 20. The alignment plate 40 may be removed from the firstmounting ring 10 and reused.

It is particularly desirable that the bolt holes 11 of the mountingrings 10 on the opposite sides of the wall 22 are aligned because thisalignment makes it easy to align transducers within the respective ringsfrom opposite sides of the wall. Given aligned rings 10 and bolt holes11, the methods and apparatus of the remainder of this invention, orother methods and apparatus, can be used to align and attache varioustransducers across the thickness of the wall 22.

In one preferred embodiment of the invention, the method, alignmentassembly 13, and alignment plate 40 described above are first used toalign mounting rings 10 and bolt holes 11 on opposite sides of a boathull wall 22. Once both mounting rings 10 are aligned and affixed totheir respective sides of the wall 22, the alignment plate 40, which hasbeen attached to a ring 10 on the submerged outside part of a ship, isremoved. At that point one of the methods described below is preferablyused to attach transducers, directly or using an intermediary layer, tothe submerged side of the boat hull wall 22.

FIG. 5 shows a preferred mounting plate installation assembly 91 formounting a plurality of transducers to a submerged surface 20 using anintermediary layer 50, as opposed to mounting individual transducersdirectly on a submerged surface. This preferred assembly 91 comprises amounting ring 10 fixed to a submerged metal surface 20, the mountingring 10 comprising a plurality of bolt holes 11 spaced around itsperiphery.

The instant preferred embodiment employs a mounting plate 50 as anintermediary layer, although other intermediary layers are possiblewithin the scope of this invention. FIGS. 4A and 4B show the top side 70and the bottom side 71 of the mounting plate 50. The bottom side 71faces towards the communication surface 20, and the top side 70 facesaway from the surface 20.

One or more transducers 52, 54 are preferably affixed to the top side 70of the mounting plate 50. Preferably the transducers 52, 54 are eachlocated within a separate depression in the top side 70 of the plate 50.In one particularly preferred embodiment, shown at FIG. 4A, a singleplate includes one large transducer 52 to send or receive power, andthree smaller transducers 54 for data communication. Persons of skill inthe art will recognize that a variety of transducers and transducerarrangements can be adapted for use with the mounting plate 50 of theinstant invention.

The mounting plate 50 preferably comprises the same metal as the metalsurface 20, such as the outside of a boat hull 22, that it will bemounted to.

The mounting plate 50 preferably includes a plurality of threaded boltholes 58 on the top side 70 of the plate 50. The plate 50 alsopreferably has both an inlet hole 53 and an outlet hole 55 extendingthrough the thickness of the mounting plate 50. Other arrangements ofinlet and/or outlet holes are also compatible with this invention,however.

The plate 50 also preferably has a channel 56 formed or carved into itsbottom side 71. The channel 56 preferably communicates with both aninlet hole 53 and an outlet hole 55. Preferably the channel 56 iscontinuous and is adapted to direct adhesive injected into the inlethole 53 to all portions of the bottom side 71 of the mounting plate 50,particularly areas near where each of the transducers 52, 54 are fixedto the mounting plate 50 above. Alternatively, or in addition, thechannels 56 can function to accept excess adhesive squeezed from betweenthe flat portions of the bottom side 71 of the plate 50 and the surface20, helping to achieve a thin, even connections in those areas.

The mounting plate 50 is sized and shaped to fit within the mountingring 10. Preferably the mounting plate has a sealant 72 at itsperiphery, such as an O-ring, that allows the mounting plate 50 to slidetoward and away from the hull surface 20 while maintaining a water-tightseal between the mounting plate 50 and the mounting ring 10 in a manneranalogous to a piston in a cylinder.

The mounting plate installation assembly 91 may also include a means forselectably moving the mounting plate 50 towards and away from the hullsurface 20. In a preferred embodiment, a pressing plate 60 (FIGS. 5, 11Aand 11B) is removably engaged to the top side 70 of the mounting plate50 using a plurality of bolts 62, a plurality of springs 64, andthreaded bolt holes 58 on the top side 70 of the mounting plate 50. Thepressing plate can preferably be removed from the assembly 91 and themounting plate 50 once the plate 50 has been attached to the hullsurface 20.

FIGS. 3A to 3D illustrate several steps (hereafter referred to as steps(1)-(4)) that can be used in attaching mounting plates 50 to submergedsurfaces 20 within a mounting ring 10. These steps generally compriseusing the plate installation assembly 91 as a piston to pump substancesinto and out of a cavity 73 or gap defined by the hull surface 20, themounting plate 50, and the mounting ring 10.

In a first preferred method, mounting plate 50 is held at a fixeddistance from the hull 22 as shown in FIG. 3A step (1), while the gap isflushed via inlet hole 53 and outlet hole 55 with an easily evaporableliquid (e.g. alcohol or acetone). This flushing will clean both the hullsurface 20 and the bottom surface 71 of the plate 50, while alsoremoving water from the gap. Once this flushing is completed, the gapwill preferably be filled completely with the evaporable liquid.

To remove the evaporable liquid, compressed air or other gas is forcedinto the gap via the inlet hole 53, pushing as much of the flushingfluid out of the cavity 73 via the outlet hole 55 as possible asdepicted in FIG. 3D step (4). Upon the extraction of as much fluid aspossible, a vacuum is immediately applied to the cavity 73, preferablyvia the outlet hole 55. It may be necessary to block one or more holes53, 55 to keep water out of the cavity 73 during the vacuuming process.

This vacuuming is adapted to accomplishes two things. First, itexpedites the evaporation of any remaining liquid. Second, it reducesthe amount of gas within the cavity 73, which reduces the chance ofbubbles later being caught within the epoxy or other adhesive.

While the vacuum is still being applied to the cavity 73, epoxy (oranother adhesive) is injected into the inlet hole 53 until it permeatesthe cavity 73 and begins to flow out the outlet hole 55 or port fromwhich the vacuum is preferably being applied. The vacuum is then removedand the epoxy flow is stopped. Ideally the cavity 73 contains onlyepoxy, and no other liquids or gasses, at this step of the process.

The plate 50 is then pressed towards and against the hull surface 20 asillustrated in FIGS. 3B and 3C steps (2) and (3), thus forcing excessepoxy to flow out from holes in the mounting plate 50, in thisembodiment holes 53 and 55. The force is preferably applied via apressing plate 60. This force is applied and maintained until the epoxyhas cured to ensure that the final bonding layer between the mountingplate 50 and the hull surface 20 is as thin and bubble-free as possible.

A second method for using the plate installation assembly 91 forevacuating the gap or cavity 73 for installing a mounting plate 50 iseven better illustrated by FIG. 3, and does not require use of a vacuum.This second method starts with the mounting plate 50 being inserted intothe mounting ring 10, resulting in a cavity show in FIG. 3A step (1)between the hull surface 20 and plate 50. At this point, the cavity 73contains seawater.

During the next step (FIG. 3B step (2)) the mounting plate 50 is pushedagainst hull surface 20, forcing the water within the cavity 73 to flowout from the outlet hole 55 or from both holes 53 and 55. The force isagain preferably applied via a pressing plate 60. Once the mountingplate 50 is pushed all the way against the hull as shown in FIG. 3C step(3), a small amount of water may remain in the interface. It ispreferable to remove even this remnant water to ensure proper coupling.

To accomplish this, an evaporable fluid, such as alcohol or acetone, isinjected via an inlet port 53 to the cavity 73 while the mounting plate50 is gently pulled away from the surface 20 as shown in FIG. 3D step(4). This brings the system back to step (1) but with the gap filledwith evaporable flushing fluid instead of seawater. It may be necessaryto temporarily cap one or more holes 53, 55 at this or other steps toprevent seawater from reentering the cavity 73.

The four steps shown at FIGS. 3A to 3D steps (1) to (4) are thenrepeated, except that pressurized air (or some other gas) is injected atstep (4) the first repeat (to remove and evaporate the evaporableliquid), and epoxy is injected at step (4) for the final repeat. At thisstep the cavity 73 should only contain epoxy.

The mounting plate 50 is then pushed towards the hull surface 20 asshown at FIG. 3B step (2), and held down in the position shown at FIG.3C step (3). Preferably this forces and holds out all gas bubbles fromthe cavity 73. The mounting plate 50 is preferably held down against thesurface 20 until a strong, thin adhesive layer has finished hardening.

FIGS. 5, 11A and 11B show the use of a pressing plate 60 connected tomounting plate 50 by bolts 62 with springs 64 for biasing the plate 50toward the hull surface 20 that can be used to perform the steps (1) to(4) of FIGS. 3A to 3D. An actuator (not shown) is preferably connectedto the pressing plate 60 via a central hole through the pressing plate60 for pulling and pushing the intermediate plate 50 as needed toperform either attachment method described above. This actuator willlikely use the mount ring as a base to provide the pushing and pullingforces needed.

FIGS. 6A to 8 illustrate preferred embodiments of an assembly 90 formounting a transducer 51 directly to a submerged surface 20, which maybe the external surface of a metal boat or submarine hull. This methodpreferably involves one or more transducers 51 being mountedindependently and directly to a submerged surface 20 within thecircumference of a mounting ring 10, the mounting ring having aplurality of bolt holes 11 and having been previously aligned with amounting ring 10 on the opposite side of the hull 22.

The preferred assembly includes a transducer 51 removably mounted to abacking 80, the backing 80 having a cup-shaped flange 82 at itsperiphery that also surrounds the transducer 51 at the periphery of thetransducer. See FIGS. 6A and 6B. Preferably the backing 80 and theflange 82 are a unitary piece. Preferably the backing 80 and the flange82 comprise an elastic substance, such as rubber, silicone, or aresilient plastic, that is flexible and that can be partially deformedwithout being permanently damaged. Preferably the elastic backing 80 andthe flange 82 together form and resemble a round suction cup. Preferablythe elastic backing 80 and flange 82 are adapted to avoid damaging thetransducer 51, such as by spreading and managing direct pressure on thetransducer, during the installation process.

The backing 80 and the flange 82 are positioned on the submerged surface20 so that the backing 80, the flange 82, and the surface 20collectively form a cavity 83 with the transducer 51 held within thecavity 83. Preferably the backing 80, the flange 82, and the transducer51 are positioned on a submerged metal surface within the diameter of amounting ring 10 previously fixed to the submerged surface 10 by weldingor marine adhesive.

The assembly 90 is adapted so that as the backing 80 is pressed towardsthe surface 20, the flange 82 deforms and creates a temporarywater-tight seal with the surface 20. FIG. 7 shows an assembly 90 beforethe backing 80 has been fully pressed towards the surface 20, with acavity 83 still clearly visible, and FIG. 8 shows an assembly after thepressing step. This pressing motion will shrink, and possibly eveneliminate, the cavity 83. The assembly may be adapted so that before thebacking 80 is pressed towards the surface 20, only the periphery of theflange 83 is in contact with the surface 20, while after the pressingboth a larger portion of the flange 83 and the transducer 51 contact thesurface 20.

A single continuous hole 84 extends through the backing 80 and thetransducer 51. The hole 84 is adapted to pass pressurized liquids andgasses originating outside the assembly 90 via tubing 92 to the space inthe cavity 83 between the transducer 51 and the submerged surface 20. Inalternative embodiments, the continuous hole 84, or a second hole, mayalso be adapted to accommodate electrical contacts reaching thetransducer. Preferably the hole 84 extends through the mutual center ofa round backing 80 and a round transducer 51, though other shapes andarrangements are possible. A hollow tube 92 removably inserted throughthe hole 84 may optionally be used to inject pressurized air and/orepoxy.

The assembly 90 may include a backing plate 86 (FIGS. 7-8) removablyconnected to the mounting ring 10 by a plurality of bolts 88 or screws(“threaded couplings”) engaged with bolt holes 11 in the mounting ring10. In a most preferred embodiment the backing plate 86 (a.k.a.“alignment plate”) has a size, diameter, and circular shape similar tothe mounting ring 10 to substantially cover the mounting ring (see FIG.10). The backing plate 86 is preferably adapted to press the elasticbackings 80 and transducers 51 within the mounting ring 10 towards thesubmerged metal surface 20, and to hold the transducer(s) 51 in placewhile epoxy is injected and allowed to harden. The backing plate 86 maybe adapted to press several elastic backing 86 and transducer 51arrangements within a mounting ring 10 simultaneously. The backing plate86 may include a plurality of holes through its thickness to accommodatetubes conveying air and adhesives, attachment means such as bolts,and/or electronic wires.

In a preferred embodiment the backing plate 86 is moved towards thesurface 20 by progressively screwing bolts 88 into the bolt holes 11 inthe mounting ring 11. As the bolts 88 are screwed into the bolt holes11, the bolts and the backing plate 86 are moved closer to the surface20. See FIGS. 7-8. Assemblies and processes using other methods ofmoving and fixing the backing plate also fall within the scope of thisinvention.

The backing plate 86 may be removed or may be left in place once thetransducer(s) 51 have been affixed to the surface 20. The backing plate86 (or “alignment plate”) may be adapted to align and position one ormore transducers 51 in defined orientations within a mounting ring 10,for example, precisely aligned with transducers on the opposite side ofa ship's hull. FIG. 10 shows a preferred embodiment where a backingplate 86 has been adapted to hold and align four transducers(transducers not visible in FIG. 10) on a ship's hull 20, and also toaccommodate electronics and wiring leading to each of the fourtransducers passing through the backing plate 86.

A preferred method of attaching a transducer 51 directly to a submergedhull surface 20 is as follows:

A transducer 51 is positioned within an elastic backing 80 and a flange82. This assembly is gently pressed against a submerged surface 20 suchthat the flange 82 of the backing 80 (which creates the “suctioncup”-like appendage) comes into contact with the surface 20 and deformsslightly to create a light water-tight seal with the hull. At thispoint, there should still be a separation between the transducer 51 andthe hull surface 20 forming a cavity 83.

Compressed air is then forced through a central hole 84 via tubing 92,pressurizing the cavity 83 within the suction cup, causing the watercontained in the cavity to be pushed out through the seal created by theflange 82 and hull surface 20. Once this step is completed, epoxy isforced into the cavity 83 between the transducer 51 and hull surface 20via the same central hole 84. Preferably, sufficient epoxy is added tofill the cavity 83 and to force the air out of the cavity. FIG. 7illustrates how this step appears in one possible embodiment.

A larger normal force is then applied to the backing 80 in the directionof the hull surface 20 to cause the flange 82 to distort further andpush the transducer 51 into contact with the wall 20. In one embodimentthis force is supplied by a backing plate 86 moving towards the surface20 by the action of bolts 88 being threaded downwards into bolt holes11. This force will greatly shrink, and potentially eliminate, thecavity 83, and will push excess epoxy out through the seal created bythe flange 82. FIG. 8 shows a side view of how this step may appear.This force should be sustained until the epoxy has completely cured.

Once the epoxy has cured, the elastic backing 80, the flange 82, and anybacking plate 86 may optionally be removed. If the elastic backing 80 isto be removed, electronics may be affixed to the affixed transducer(s)51 at this point.

The Mounting Ring

One advantage of the present invention is that it adapts a singlehardware concept, the mounting ring 10, for several transducer mountingmethods, and also provides a method of aligning mounting rings across abarrier where both sides of the barrier cannot be viewed simultaneously.

It will be appreciated that the basic ring concept can be variedsomewhat without departing from the invention. Different materials,different size rings, and even “rings” having non-circular shapes can beadapted for use with the methods and assemblies described herein. Theterm “mounting member” is broader term referring generally to hullattachments that have the same general form and function as a “mountingring” but which may or may not take the form of a circular section of acylinder. The preferred embodiments employ a circular ring structureresembling a section of a hollow cylinder purely for design simplicity,and this invention is not limited to round configurations.

The mounting ring may be attached to the communication surface by themost convenient means available. In the case of boat and submarinehulls, this will often be via welding or marine glue. The mounting ringis preferably thick enough to support six or more ⅜inch-16 threads/inchbolt holes for connection of additional hardware, and strong enough toserve as a foundation which all other mounting hardware can connect to.The preferred outer diameter was chosen to be 12 in., with the ringthickness and height both measuring 0.75 in.

Rotational Alignment Across a Hull Wall

For the transducer communication systems to operate effectively, it isnecessary to ensure that the mounting rings are coaxially androtationally aligned on either side of the hull. To achieve this,ultrasonic peaking may be done using transducers, such as untrasonic NDTtransducers or piezoelectric transducers. In “peaking” a firsttransducer fixed at a point on one side of a wall transmits a pulsetrain, while a second transducer on the opposite side is moved tovarious locations to find the location corresponding to the maximumreceived amplitude. The location of maximum amplitude corresponds to theposition of the first transducer on the opposite side of the wall.

Any device which emits signals that can be accurately located on theopposite side of the barrier may be used in place of the preferredultrasonic transducers for alignment.

A single peaked axially-aligned transducer would suffice for simplecoaxial alignment of the mounting rings, but it is preferable to havealignment of the screw or bolt holes 11 on the mounting rings as well toaid in individual transducer angular alignments. Thus, it is highlydesirable to achieve rotational alignment, which requires aligning aminimum of two transducers and/or peaks.

FIGS. 2A and 2B show a preferred assembly employing two transducers torotationally align mounting rings 10 across the thickness of a wall. Theassembly consists of an alignment plate or “alignment arrangement” 40which is attached to the mounting ring 10 via two screws 42, preferablyon the submerged outside surface 20 of a hull. At a symmetric separationfrom the central axis, two transducers 44 with strongly-damped backingsare attached by screws 46 to the alignment plate. The transducers may beattached to backings that receive the screws 46. The alignment plate andtransducer backings are adapted such that the transducers 44 may beeffectively forced against the hull or other surface 20.

The term “alignment arrangement” 40 refers to an arrangement comprisinga plurality of transducers and for temporary attachment to a mountingring 10 as described above for alignment across a hull wall. An“alignment arrangement” may take a variety of shapes and includes, butis not limited to, the “alignment plate” of the preferred embodiment asshown in FIG. 2A and described elsewhere.

The contact between the alignment transducers 44 and the hull istemporary and does not necessarily need to be optimized. As such, eitherno coupling agent is required, effectively using the surrounding wateras the couplant (if used on the exterior of the hull, which ispreferable), or a water non-soluble acoustic couplant may be applied tothe interface.

A single movable transducer may be used to determine the positions ofthe two transducers 44 from the opposite, preferably internal side ofthe hull wall 24 using signal peaking. Once the location of bothtransducers are marked on the opposite side 24 of the wall, and knowingthe locations of the transducers 44 connected to the already-attachedmounting ring 10, the second mount ring may be rotationally aligned bylining up the marked transducer locations on the inner hull wall 24 withtheir appropriate reference points to the second mounting ring.

Alternatively, a second mounting ring engaged to a second alignmentplate in a mirror-image configuration, having the same number of and amirror-image arrangement of transducers as the first alignment plate maybe aligned on the opposite side of the wall by simultaneously peaking aplurality of transducers.

If the transducers and mounting ring are arranged such that they showrotational symmetry, then using the two markings may align alltransducers with some identity ambiguity. For example: if there were 2communication crystals 44 (crystal A and crystal B) set at the sameradial distance from the center of the first mount ring 10, andseparated by 180 degrees, this alignment procedure would not distinguishbetween the alignment of crystals A or B vis a vis the opposite side ofthe wall 24. This can easily be compensated for, however, by a manualpost-alignment connection of each transducer to its correspondingelectronics on the inside of the ship.

Alternatively, a third transducer providing a third peaking point may beused to prevent any mirror-image ambiguity.

Mounting Transducers Via Intermadiary Layer

Transducers may be mounted to a submerged surface employing anintermediary layer between the transducers and the wall interface,preferably in conjunction with a mounting ring 10. This intermediarylayer is preferably a large metallic plate, most preferably constructedof the same material as the hull. The plate can be attached to a hullvia a water-resistant adhesive bond, preferably epoxy.

The intermediary plate has one or more transducers pre-attached to it ina laboratory or factory environment, and is preferably sized to fitwithin the mounting ring 10 it is to be used with. Those of skill in theart will recognize that a variety of transducer-related electronics maybe advantageously affixed to such plates for later underwater mounting.Using this method, once two mounting rings have been rotationallyaligned across a hull wall, multiple transducers pre-mounted on platescan easily be aligned across the same hull wall by installing the plateswithin the aligned rings using the rotationally aligned bolt holes 11.

For the intermediary plate configuration, two general methods forremoving water from the plate-hull interface, and then applying epoxy tothe interface, are proposed. For both methods, it is assumed that theplate (which may be identical in each case) and/or the mounting ringhave inlet 53 and outlet 55 ports for fluids and gases to flow into andout of the gap between the plate and hull. A variety of outletarrangements may be used, but it is preferable to use at least twooutlets, and that the outlets be spaced apart. Furthermore, the plateand the mounting ring should be sealed in some fashion to prevent theback-flow of seawater into the gap or cavity 73.

The first preferred method for prepping the hull 22 surface 20 andmounting plate 50 surfaces and applying the epoxy calls for the mountingplate to be held at a fixed distance from the hull, while the cavity 73is flushed with an easily evaporable liquid (e.g. alcohol or acetone)which will in effect clean both the hull and plate surface while alsoremoving water from the gap. Once this flushing is completed, the gapwill be filled completely with said liquid.

To remove the evaporable liquid, compressed air (or some other gas) isforced into the gap, pushing as much of the evaporable flushing fluidout as possible. The evaporable liquid can be removed from the cavitymuch more completely and efficiently using forced air and vacuums thanwater, especially sea water, could be. The evaporable liquid will alsobe substantially free from contaminants, unlike ocean, lake or riverwater.

Upon the extraction of as much evaporable fluid as possible, a vacuum isimmediately applied to the cavity 73 or gap via one or more ports orholes 53, 55. This vacuum accomplishes two things. First, it expeditesthe evaporation of any remaining flushing liquid. Second, it reduces theamount of gas within the gap, which in turn reduces the chance ofbubbles being caught within the epoxy layer between the plate and thehull wall. While the vacuum is still being applied, epoxy is injected,preferably via the inlet port 53, until it permeates the gap 73 andbegins to flow out of the outlet port 55 at which the vacuum is beingapplied. Once this occurs, the vacuum is then removed and the epoxy flowis stopped. The mounting plate 50 is pressed towards and against thehull surface 20, allowing excess epoxy to flow from the ports. The forceused to press the plate against the hull should continue to be applieduntil the epoxy has cured to ensure that the bonding layer is as thin aspossible and to keep water out.

The force may be applied against the mounting plate 50 using essentiallyany means. Preferably, a pressing plate 60 coupled to a hydraulicmechanism is used. Attachments to bolt holes 11 in the mounting ring 10could also be adapted to hold down the mounting plate 50.

A second preferred embodiment for evacuating the gap 73 and applying theepoxy was developed to remove the need for a vacuum to be applied. Themounting plate 50 and the mounting ring 10 are used in a mannerresembling the action of a fluid piston pump, where the plate 50 acts asa piston. A sealant 72, such as an O-ring or a viscous, water-resistantlubricant, is preferably employed to prevent water from penetrating thejunction between the mounting plate and the mounting ring, while stillallowing the plate to move towards and away from the hull surface withinthe mounting ring. A simplified order of events for this method ispresented in FIG. 3. Those of skill in the art will appreciate that somevariation in these steps is possible to achieve the same or similarresult.

The major steps of this second preferred method are shown in FIGS. 3A to3D. The method begins with the plate 50 being inserted into the mountingring 10, resulting in a gap or cavity 73 between the hull surface 20 andmounting plate, the cavity containing seawater. FIG. 3A step (1). Duringthe next step (FIG. 3B step (2)) the plate is pushed towards and againstthe hull, forcing the water within the gap to flow out of the gap 73through the outlet port 55 and/or any other available openings. Once themounting plate 50 is pushed all the way against the hull surface (FIG.3C (3)), a small amount of water may remain in the interface, but shouldpreferably still be removed to ensure proper coupling.

To accomplish this, an evaporable fluid, such as alcohol or acetone,should be added to the gap 73. This can be achieved by injecting thefluid into the inlet port 53 while the mounting plate 50 is pulled awayfrom the wall (FIG. 3D step (4)). It may be necessary to block certainopenings to keep seawater from reentering the cavity. This step bringsthe system back to FIG. 3A step (1), except that the gap is now filledwith evaporable flushing fluid instead of seawater. The same 4 steps arethen repeated using forced air (or some other gas) to evaporate theremaining evaporable liquid, and again repeated with epoxy. It may benecessary to keep the forced air turned on during steps (2) and (3) ofthe forced air cycle to keep water out of the cavity. Once the cavity 73is filled with epoxy in a manner resembling FIG. 3C step (3), the excessepoxy having been forced out in the previous step, the mounting plate 50should be held in place while the epoxy cures.

This second preferred method accomplishes the same end result as thefirst method, except instead of controlling the amount of material inthe gap via forced liquids, forced fluids, and a vacuum (applied to acavity 73 at mostly constant volume), liquids and gasses are added orremoved by increasing and decreasing the volume of the gap or cavity 73(at constant pressure) and by forcing substances into the cavity.

Various combinations of these methods can be readily employed to achieveremoval of water from the cavity 73, filling the cavity with bubble-freeadhesive, and forcing and holding the plate 50 into contact with thesurface 20 while a permanent bond forms. Methods that combine the use ofa vacuum and repeatedly altering the volume of the gap are also withinthis scope of this invention, and will be obvious to individuals ofskill in the relevant arts.

Intermediary Mounting Plate

FIGS. 4A and 4B show a preferred mounting plate 50 that can be usedwith, for example, either of the plate mounting methods described above.The top side 70 carries one or more transducers and the bottom side 71of the mounting plate is preferably attached to a hull surface.Preferably, two plates similar to the example shown in FIGS. 4A and 4Bare aligned and attached on opposite sides of a wall to communicatepower and signals through the wall.

The preferred transducer mounting plate 50 shown in FIGS. 4A and 4Ballows for the mounting of three data communication transducers 54 andone large power transducer 52. In this preferred representation, thereis more detail shown than is required for a mounting plate usable forthis invention.

Each of the transducers 52, 54, preferably sits in a depression in thetop 70 of the plate 50. This feature is meant to improve the system'stransducer-transducer isolation by eliminating the path for surfaceacoustic waves (SAWs) to travel between transducers.

The two smaller holes seen in FIGS. 3A to 4B represent the input 53 andoutput 55 ports for fluid and gasses to flow into and out of the cavity73 under the mounting plate 50 during the installation process. More orfewer ports may be used, but two ports spaced apart are preferred.

On the bottom side 71 of the plate, an optional snaking groove or“continuous channel” 56 is shown. Such grooves may be useful for methodswhere epoxy is injected between a mounting plate 50 and the hull surface20 when they are already pressed together leaving little space betweenthem. Preferably, the channel 56 is a single continuous, snaking paththat leads from the input hole 53 to the outlet hole 55 and is adaptedto guide epoxy between those holes, although other configurations may beused to distribute epoxy. The channel is preferably adapted to make surethat epoxy reaches the entire interface between the mounting plate 50and the surface 20, particularly locations near the transducers 52, 54.

FIGS. 4A and 4B do not specifically show any means for creating a sealat the wall interface between the mounting plate 50 and mounting ring10. It is preferable, however, to employ some sealant that allows theplate to move past the ring 10 like a piston while preventing water frompassion through the interface. This seal could be accomplished with theuse of an O-ring, certain viscous lubricants, or other traditionalmethods.

Preferred Hardware for Maneuvering Mounting Plate

Three holes 58 are also shown on the top 70 of the plate in FIG. 4A.These holes are most preferably threaded to allow for the connection ofbolts to the mounting plate 50, and may be used to temporarily attach apressing plate 60 to the mounting plate 50 (see FIG. 5) by bolts 62. Thehardware for pushing and pulling the mounting plate 50 during theunderwater adhesion process may be, in a preferred embodiment, a smallerpressing plate 60 with a central hole and preferably three non-threadedbolt holes to match those 58 on the plate 50. The bolt holes on thispressing plate 60, however, are clearance holes. A bolt 62 is passedthrough this hole and screwed into the transducer plate 50, preferablywith 1 inch die springs 64 positioned between the plates 50, 60, asillustrated in FIGS. 5. and 11. The central hole in the pressing plate60 is meant for the connection of some means to push and pull the plate.This may be accomplished with, for example, a simple hydraulic system.

Pressure on the pressing plate 60 towards the surface 20 is transferredto the transducer mounting plate 50, which is then moved such that itcomes into contact with the hull surface 20. At this point, the springs64 may begin to compress and bend, allowing the mounting plate to pivotabout its first surface 20 contact point. This preferably causes themounting plate to come to an alignment where the transducer mountingplate 50 is at an optimum, minimum angle to the hull surface 20 (whichwill often have some curvature to it). FIGS. 11A and 11B show enlargedsectional views of a pressing plate 60 pushing a mounting plate 50against a hull surface 20 before (left) and after (right) springcompression. Here, it is shown that as the mounting plate 50 is pushedup against the hull, the bolt 62 is allowed to move away from thepressing plate 60, while force is applied through the compression of thespring 64. To pull the mounting plate back, the pressing plate is movedbackwards into contact with the heads of the bolts 62, at which point abackwards force would also be applied to retract the transducer plate.

At the point when epoxy is applied to the plate-hull interface, thesprings 64 pressed against the mounting plate 50 should be held incompression until the epoxy has cured, at which point the applied force,the three bolts 62, the springs 64, and the pressing plate 60 can all beremoved, leaving only the transducer plate 50 attached to the hullsurface 20. At this point additional electronics for use with thetransducers may be attached to the mount plate.

The method of moving mounting plates within the mounting ring using apressing plate, holes in the top side of the mounting plate, and springsdescribed above is merely a preferred embodiment.

Mounting Transducers Via Direct Attachment to Hull

While the underwater coupling methods presented above are advantageousin that multiple transducers may be mounted to a plate prior tosubmersion, and in that only one interface needs to be coupled(plate-to-hull), there are also advantages to attaching the transducersdirectly. The additional complexity associated with direct transducermounting methods may be justified, however, because direct attachment ofthe transducers to the hull allows better communication and moreefficient power transfer. As a result, additional methods for couplingtransducers to the hull directly and individually have been developed.

The instant design for direct attachment involves temporarily mountingthe transducers to a highly elastic backing (i.e., rubber, silicone,resilient plastics etc.). This backing, an example of which is shown inFIGS. 6A and 6B, is preferably similar to a suction cup, with thetransducer held in the center of its cavity, although other shapesallowing for similar water-resistant seals may also be used. Both thebacking and the transducers for this design have a hole, preferablythrough their axes. This hole is used as a port for injection of air,epoxy, and potentially other substances. Introducing a small holethrough the center of the transducers has a negligible effect on itsoverall piezoelectric response.

Using this method, transducers may be applied to the hull individually,but the issue of arranging and aligning the transducers is still aconcern as manual placement of the piezos (or other transducers) mayresult in inaccurately aligned channels. To allow the direct transducerattachment method to have a predefined arrangement of transducercrystals on the hull, it is possible connect the transducer-backingassemblies to an alignment plate or backing plate 86 which will allowfor strict position definition. Further, if an alignment plate isinvolved, the mechanisms to apply the compressed air and epoxy (e.g.,tubing 92) may be integrated to allow for a simplified mountingprocedure.

FIG. 10 shows a preferred direct-attachment transducer assembly that maybe implemented using this methods and apparatus of this invention. Abacking plate 86 has been adapted to hold and align four transducers(transducers not visible in FIG. 10) on a ship's hull 20. Tubes 92 areshown entering the backing plate 86 at four points, each leading to atransducer mounted to the hull surface 20 below. The backing plate isattached to the mounting ring 10 via six screws. This sort of assembly,including the backing plate 86, may be left in place permanently.Variations on this preferred backing plate accommodating, for example,different transducer numbers and arrangements, different electronics,different mounting ring shapes, and different surfaces, also fall withinthe scope of this invention.

Alternatively, backing or alignment plates 86 can be employed onlyduring the steps of aligning and/or pressing the backings 80 andtransducers 51 on the surface 20, and eventually be removed from theassembly 90.

In the preferred configuration of FIG. 10, the synchronous attachment ofthree communication and one power transducer may be accomplished. Todistribute compressed air and epoxy (for example, pursuant to the directmounting method described above) to each of the four transducer mountlocations, tubing 92 is routed from a manifold (not depicted, preferablylocated in upper-left of FIG. 10) to each mount location via holesthrough the backing alignment plate 86. The tubing 92 may be held inplace, for example, by compression nuts on the alignment plate.

The elastic backings 80 (shown connected to the alignment plate in FIG.7) are preferably attached rigidly to the backing plate 86 via screwsthrough the backing.

To provide the compressive force to the assemblies required forattachment, a gap is preferably left between the backing plate 86 andthe mounting ring 10 during initial assembly, as shown in FIG. 7, sothat the backing 80 is not fully pressed towards the surface 20. Thecavity 83 between the backing 80 and the surface 20 is preferably heldconstant during the compressed air flushing and the subsequentapplication of epoxy. Once the epoxy is applied, the screws or bolts 88which connect the backing plate 86 and mounting ring 10 may betightened, causing one or more elastic backings 80 to push theirrespective transducers 51 against the wall 80. This will also push anyexcess expoxy out of the gap or cavity 83 and shrink or eliminate thecavity. The coupling force may be sustained throughout epoxy curing inthis embodiment merely by leaving the backing plate 86 screwed in place(see FIG. 8).

In an alternative preferred embodiment, tubing 92 for deliveringcompressed air and epoxy is adapted to fit within the backings 80, suchas through a central hole 84. Using removable tubing to deliver epoxyreduces the risk that unwanted epoxy bonds will form between thetransducer, the backing, and/or the backing plate. The hole 84 ispreferably designed both to create a seal around the tubing (if thetubing is used and inserted correctly) and a pathway to the gap betweenthe transducers 51 and surface 20. Preferably the tubing can be removedfrom the hole 84 after all necessary epoxy has been delivered. Mostpreferably the tubing is removed, via loosening of the compression nuts,once the bolts 88 holding the backing plate 86 and the backings 80 downhave been tightened, but before the epoxy has cured.

Once the tubing 92 is removed, the hole 84 may be repurposed, such asfor inserting electronic elements to contact the transducer 51.

Alternatively, the flexible backing 80 and the alignment or backingplate 86 may be removed and reused for future installations after theepoxy hardens. If the elastic backings are rigidly connected to thebacking plate, removal of the backing plate may be affected by thematerial composition of the elastic backings, specifically, the abilityof the backing to resist adhesion to any stray epoxy it may come intocontact with. It is preferable that the backing 80 and flange 82 becomprised of or coated with materials that will not be bound by epoxy.

If the backing plate and elastic backings are removed, only thetransducers will be left on the submerged hull. At this point, theelectronics required to operate the system may be attached. This willrequire a seawater submersible electrical connector or another method ofelectrical connection. The mounting design may be adjusted to allow theelectronics package to be mounted simultaneously with the transducers,which is within the capacity of persons of skill in the art.

While several specific embodiments and aspects of the invention havebeen shown and described in detail to illustrate the application of theprinciples of the invention, it will be understood that the inventionmay be embodied otherwise without departing from such principles.

What is claimed is:
 1. A mounting plate installation assembly formounting one or more transducers on a submerged external surface of awatercraft, the assembly comprising: a mounting member fixed to thesubmerged surface, the mounting member projecting outward from thesubmerged external surface of the watercraft; a mounting plate having atop side facing away from the submerged surface, and a bottom sidefacing towards the submerged surface; a plurality of transducers fixedto the mounting plate; the mounting plate having an inlet hole and anoutlet hole through its thickness, such holes being adapted for passinggasses and liquids between top and bottom sides of the mounting plate;the mounting plate being sized to fit within the mounting member; andthe mounting plate and the mounting member being positioned so that themounting plate slides within the mounting member towards and away fromthe submerged surface, while maintaining a substantially water-tightseal between the periphery of the mounting plate and the mounting;wherein said submerged surface is a planar external surface of thewatercraft which is in direct contact with a body of water, and theassembly is also in contact with the body of water; and wherein theassembly is external to the watercraft, and does not penetrate theexternal surface of the watercraft.
 2. The assembly as claimed in claim1, wherein the mounting member is a mounting ring having the shape of asection of a hollow cylinder, and wherein the mounting plate issubstantially round.
 3. The assembly as claimed in claim 1, wherein thebottom side of the mounting plate comprises a channel adapted to directadhesive from the inlet hole to other areas of the bottom side of themounting plate; the channel being an elongated concave channel formedinto a planar surface of the mounting plate and having at least one endin fluidic connection with the inlet hole.
 4. The assembly as claimed inclaim 1, further comprising a sealant at an interface of the mountingplate and the mounting member, the sealant being adapted to facilitatemovement of the mounting plate towards and away from the submergedsurface while maintaining a water-tight seal between the periphery ofthe mounting plate and the mounting member.
 5. The assembly as claimedin claim 1, wherein the mounting member comprises a plurality ofthreaded holes spaced about its periphery.
 6. The assembly as claimed inclaim 1, wherein the plurality of transducers are each fixed in arespective one of a plurality of separate depressions on the top side ofthe mounting plate.
 7. The assembly as claimed in claim 1, wherein thetop side of the mounting plate comprises a plurality of threaded holes;the assembly further comprising a pressing plate removably engaged tothe top side of the mounting plate using a plurality of said threadedholes; and the pressing plate being adapted to selectably push and pullthe mounting plate towards and away from the submerged surface.
 8. Theassembly as claimed in claim 7, wherein the pressing plate isnon-rigidly engaged to the top side of the mounting plate using aplurality of threaded couplings engaged with the threaded holes of themounting plate; further comprising a plurality of springs positionedbetween the pressing plate and the mounting plate, the springs beingadapted to transfer pressing pressure from the pressing plate to themounting plate in the direction of the external surface of thewatercraft.
 9. The assembly of claim 1: wherein the submerged externalsurface of a watercraft is a submerged area of a hull of one of a boatand a submarine, and wherein the mounting member is attached to the hullby one of welding and marine glue.
 10. The assembly of claim 1: whereinthe mounting member consists of a metal ring having a plurality ofthreaded holes therein which is welded to the external surface of awatercraft.
 11. The assembly of claim 1: wherein a second mountingmember is mounted on an internal surface of the watercraft directlyopposite and aligned with said mounting member on the external surfaceof the watercraft; wherein the second mounting member and the mountingmember on the external surface of the watercraft have substantially thesame shape.
 12. The assembly of claim 1: further comprising adhesivebetween the mounting plate and the external surface of the watercraft.13. The assembly of claim 1: wherein the mounting member is in the formof a ridge extending out from the external surface of the watercraftinto the water; wherein the mounting member forms a closed shape whichframes a planar area of the external surface of the watercraft; whereinthe mounting member has a flat surface which faces away from the surfaceof the watercraft and which fully surrounds and frames said planar areaof the external surface of the watercraft; and wherein a plurality ofthreaded holes are spaced on the flat surface.
 14. A mounting plateinstallation assembly for mounting one or more transducers on asubmerged surface, the assembly comprising: a mounting member fixed tothe submerged surface, the mounting member projecting outward from thesubmerged surface into a body of water; a mounting plate having a topside facing away from the submerged surface, and a bottom side facingtowards the submerged surface; a plurality of transducers fixed to themounting plate; the mounting plate having both an inlet hole and anoutlet hole through its thickness, such holes being adapted for passinggasses and liquids between top and bottom sides of the mounting plate;the mounting plate being sized to fit within the mounting member; andthe mounting plate and the mounting member being positioned so that themounting plate slides within the mounting member towards and away fromthe submerged surface, while maintaining a substantially water-tightseal between the periphery of the mounting plate and the mounting. 15.The assembly according to claim 14, wherein the submerged surface is anexternal surface of a watercraft which is in a body of water.
 16. Theassembly according to claim 14, wherein the assembly does not penetratethe external surface.